I think you paid too much.
Just kidding.
From "The History of Steel in Eastern Asia" by the Macao Museum of Art:
"Mandaya spears are double edged with a central ridge and a distinct V-point. Spearheads are socketed to the shaft instead of a tang. Occasionally there is fine chiseling and paneling (#29). "
This one seems to fit the bill. Can't tell from the pics if it's socketed or tanged, though.
Nice!
Steve